Bonobo squeaks provide a hint to early evolution of speech

In a variety of contexts the wild bonobos use a single high pitched call showing flexibility in the way they communicate and this was considered to be unique to humans. This is the conclusion from a study by Swedish and UK Psychologists.

Although Bonobos are closely related to chimpanzees and humans, their wild communication has not been studied enough. According to researchers, the present findings take the development of vocal calls free from context back to our shared ancestor with the bonobos some 6 to 10 million years ago.

For long, the assumption was that non human primates including the bonobos and chimpanzees could communicate using only calls that were linked to specific states of emotion such as aggression, barking or screaming in alarm.

Use of a singular vocal signal in varying context known as functional flexibility was reckoned as the ability exclusive to humans and developed in very stage of human life. For instance, babies as young as 3 of 4 months have used growls and squeals across a wide array of situations, irrespective of whether they are distressed, happy or neutral. These are also parallel to other noises obviously tied to specific emotions like laughing or crying.

A similar phenomenon was noticed by Dr. Zanna Clay from University of Birmingham among bonobos when she was studying in Congo. Apart from the usual barks, screams, grunts and pants she also heard a specific squeaking sound or peep that was used all over the area. This peep appeared very flexible and one could find this in nearly every context that a bonobo could be experiencing.

The researchers therefore collected recordings of thee peeps produced in multiple contexts.

Dr. Clay in association with colleagues from University of Neuchatel, Switzerland found that peeps used in multiple neutral and positive situations like traveling or feeding were acoustically identical. This gains importance because it is possible to derive the meaning of the peeps partly from its context. Dr. Clay explains that on its own the peeps don t tie themselves strongly to any one meaning.

Therefore, it appears that this type of structural flexibility considered to be a major building block for human language is not unique and has in fact turned up ages ago within our family tree. Our ability of flexible signaling was possibly much older than merely the human lineage, says Dr. Clay.